340 blocks, whats the damage on the wallet?

If you only want a 340 , the siamese block will work , but would be overkill.
The 340 replacement block is a very stout piece , with the same bore restrictions as a 340 , but much beefier bottom end.
I am continuously astounded by the price of production 340's.......but it is what the market will bear. If you spend 500 for one that needs machne work , you are in the neighborhood of the resto block , which still needs machine work , but is far stronger.
If you aren't building for north of 500 h.p. , this is overkill.
If it were me , I'd do a 416 and leave 340 badges on the car.........keep them guessing.